Brush holder for electric machine



Sept. 18, 1956 J- D. M DONALD BRUSH HOLDER FOR ELECTRIC MACHINE Filed Dec. 23, 1955 f)? 1 677 for; Jmes D M0 Dona/0,

by rwiwfla H/s Attorney United States Patent BRUSH HOLDER FOR ELECTRIC MACHINE James D. McDonald, Erie, Pa., assignor to General Electric Company, a corporation of New York Application December 23, 1955, Serial No. 555,003

6 Claims. (Cl. 310-239) My invention relates to brush holders such as are used in dynamoelectric machines, and more particularly to brush holders which are adjustable to compensate for commutator wear.

Commutators for large size dynamoelectric machines wear down during use resulting in an increase in the distance between the brush holder and the commutator so that the brush holder does not give adequate support to the brush tip near the commutator. As the distance between the commutator and the brush holder increases, the tendency for damaging vibrations in the tip of the brush is increased. To compensate for this reduction in commutator diameter, the brush holder should be moved closer to the commutator for good brush performance. In the past, this adjustment has been obtained by various types of adjustable clamps with elongated clamping apertures which are subject to loosening by vibrations. With these slotted brush holders, the accurate location of the brush circumferentially of the commutator, as required for good commutation and speed regulations, is difiicult to obtain.

An object of my invention is to provide a reliable and vibration proof adjustable brush holder.

A further object of my invention is to provide a locking plate for a brush holder to prevent slippage thereof.

According to my invention, the damaging efiect of vibrations which would tend to move an adjustable brush holder is eliminated by the use of an arm pivotably mounted on an insulating stud located at a point tangential to the commutator at the point of brush contact. The angular positioning of the arm adjusts the location of the brush relative to the commutator and is accomplished by a plurality of equally spaced recesses in the arm and mating detents in a locking plate which is securely fastened to a second insulating stud.

For a better and more complete understanding of my invention, together with additional objects and advantages thereof, reference should now be had to the following detailed description taken in conjunction with the accompanying drawings. The features of novelty will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In the drawing,

Fig. 1 is a top plan view partially in section of the brush mechanism embodying my invention;

Fig. 2 is a side plan view of the brush holder shown in Fig. 1 when the commutation is new;

Fig. 3 is a side view of the brush holder when the commutator is worn;

Fig. 4 is a detail view of the locking plate of my invention; and

Fig. 5 is a partial view of the brush holder showing one method of locating adjustment recesses.

In the drawing, I have shown a brush holder arm 1 secured to insulating studs 2 and 3 which are in turn secured to a stationary support member or end wall 4 of a dynamoelectric machine. The brush holder arm 1 is provided with a central brush passageway 5, an aperture 6 on one side thereof and an aperture 7 on the other side thereof. Bolts 8 and 9 pass through each of the apertures 6 and 7 respectively to securely clamp the arm 1, and the studs 2 and 3 to the end wall 4 of the machine. In order that a brush 10 may not be grounded through the bolts 8 and 9, I prefer that these bolts be an insulating material or be provided with an insulation insert therein (not shown). Also, it is preferable to provide locking means for these bolts such as the lockwashers 8a and 9a shown.

In order to accurately position the brush 10 circumferentially relative to a commutator 12, the aperture 6 is machined to fit the unthreaded portion of the bolt 8 with as small clearance as practicable as shown in Fig. 1. Also, it should be noted in Fig. 5 that the aperture 6 is centered on a tangential extension 11 drawn from the point of contact between the brush 10 and the commutator 12 so that the radial adjustment which pivots the arm 1 about the bolt 8 will not materially change the point of circumferential contact point between the brush 10 and the commutator 12.

In order to provide radial adjustment of arm 1 relative to the stud 3, the aperture 7 is purposely designed to be larger than the bolt 9. However, I have found that the use of loose slots, depending entirely on the friction between the bolt and the slot to maintain the brush holder in position, is generally not satisfactory, and that there is a tendency of the bolt to allow slippage of the brush holder because of the continuing pressure of the brush springs 13 and/or vibrations in service.

Therefore, I have designed an oblong locating plate 14 (Fig. 4) which is provided with a central aperture 15 and detents 17 near the extremities thereof. The aperture 15 is machined to provide a very small clearance around the bolt 9. Thus, when the bolt 9 is tightened in place, the locating plate 14 is positively located. The detents 17 fit snugly into one of several pairs of equally spaced apart apertures or recesses 20, 21 or 22. These pairs of recesses are arranged to receive the detents 17 in each pair to center the plate 14 an equal distance from the bolt 8, but to vary the location of the bolt 9 within the aperture 7 thus controlling the position of the arm 1 relative to the commutator. It is easily seen that when the detents 17 are positioned within one of the pairs of recesses, the radial position of the arm 1 also is positively located.

Where the commutator 12 is new and full size, I prefer to position the detents 17 in the pair of recesses 20 (Fig. 2) which will securely locate the arm 1 at the point furthest from the commutator 12 thus providing a predetermined distance between the end of the passageway 5 and the commutator 12. In Fig. 3 the detents 17 are positioned within the pair of recesses 22 so that the arm 1 is moved a fraction of an inch closer to the commutator 12a of the particular machine shown. This position is used when the commutator is considerably worn thus providing the same desired predetermined distance between the passageway 5 and the worn commutator 12a.

I have also shown an intermediate pair of recesses 21 for positioning the brush holder an intermediate distance to be used when the commutator is partially worn to provide the desired predetermined distance between the brush holder 1 and the commutator. Referring now to Fig. 5, I have shown one method of locating the pairs of recesses. I first determine the amount of allowable commutator wear for aparticular dynamoelectric machine. This distance A is then projected from the center line of the brush to the region of the aperture 7 as the arc B. Allowance is made for the size of the bolt 9 and a suitably sized aperture 7 is made in the arm 1. The are B is then bisected or otherwise divided into 3 equal segments within the projection region, and equal construction circles 21 and 22' having diameters equal to the distance between the center lines of the detents 17 are drawn with their centers at the ends of each of the segments. In order to positively locate the pairs of recesses 20, 21 and 22, the diameters 20", 21 and 22" are drawn, with the ends of the diameters being the center of the recesses. It is obvious that, with a larger locating plate 14 and/or a more elaborate arrangement of the pairs of recesses, it would be possible to provide several more positions, without departing from the true spirit of my invention, while maintaining the brush holder securely.

While I have shown and described a particular embodiment of my invention, modifications thereof will occur to those skilled in the art. I intend by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A brush holder comprising an arm provided with a passageway therethrough to accommodate a brush, a pair of bolts adapted to secure said arm to a supporting member, said arm being pivotably mounted on one of said bolts, said arm being provided with an enlarged aperture adapted to fit loosely the other of said bolts, said arm being provided with a plurality of pairs of recesses surrounding said aperture, and a locking plate provided with a central opening adapted to fit tightly said other bolt and provided with a pair of detents adapted to selectively engage one pair of said recesses whereby said arm may be secured in a plurality of angular positions.

2. A brush holder comprising an arm provided with a passageway therethrough to accommodate a brush, a bolt adapted to pivotably support said arm, said bolt be ing secured to a supporting member at a point on the tangential line of a commutator drawn from the point of contact between said brush and said commutator, an other supporting bolt, said arm being provided with an enlarged aperture adapted to fit loosely said other bolt, said arm being provided with a plurality of pairs of recesses surrounding said aperture, and a locking plate provided with a central opening adapted to fit tightly said other bolt and provided with a pair of detents adapted to selectively engage one pair of said recesses whereby said arm may be secured in a plurality of angular positions.

3. A brush holder comprising an arm provided with a central passageway therethrough to accommodate a brush, a bolt adapted to pivotably support one end of said arm, said bolt being secured to a supporting member to allow the pivoting of said arm from a point on a tangential extension line of a commutator drawn from the point of contact between said brush and said commutator, another supporting bolt, said arm being provided with an enlarged aperture at its other end adapted to fit loosely said other bolt, said arm being provided with a plurality of pairs of recesses surrounding said aperture, and a locking plate provided with a central opening adapted to fit tightly said other bolt and provided with a pair of detents adapted to selectively engage one pair of said recesses whereby said arm may be secured in a plurality of angular positions.

4. A brush holder comprising a pair of spaced apart insulating studs secured to a stationary member, the first of said studs being centered at a point substantially on a tangential extension line of a commutator drawn from the point of contact between a brush and said commutator, an arm provided with a passageway therethrough to accommodate said brush, a pair of bolts adapted to secure the brush holder to said pair of studs, said arm being pivotably mounted on one of said bolts secured to said first stud, said arm being provided with an enlarged aperture positioned over the second of said pair of studs and adapted to fit loosely the other of said bolts, said arm being provided with a plurality of pairs of recesses surrounding said aperture, and a locking plate provided with a central opening adapted to fit tightly said other bolt and provided with a pair of detents adapted to selectively engage one pair of said recesses whereby said arm may be secured in a plurality of positions relative to said commutator.

5. In a dynamoelectric machine having a commutator and a brush adapted to contact said commutator, a brush holder comprising a pair of spaced apart insulating studs secured to the machine, the first of said studs being centered at a point substantially on a tangential extension of the commutator drawn from the point of contact between the brush and the commutator, an arm provided with a central brush passageway therethrough, the second of said studs being positioned adjacent to the end of said arm remote from said first stud to provide a maximum leverage relative to said passageway, a pair of bolts adapted to secure said arm to said pair of studs, said arm being provided with a first aperture centered over said first stud and adapted to fit tightly one of said bolts, said arm being provided with a second enlarged aperture positioned over said second stud and adapted to fit loosely the other of said bolts, said arm being provided with a plurality of pairs of equally spaced apart recesses surrounding said second aperture, and a locking plate provided with a central opening adapted to fit tightly said other bolt and provided with a pair of detents adapted to selectively engage one pair of said recesses, said pairs of recesses being arranged in conjunction with said plate to secure said other bolt in a plurality of positions relative to said second aperture whereby said brush holder may be secured in a plurality of angular positions relative to said commutator.

6. In a dynamoelectric machine a commutator and a brush adapted to contact the commutator, a brush holder comprising, a pair of spaced apart insulating studs secured to the machine, the first of said studs being centered at a point substantially on a tangential extension line drawn from the point of contact between the brush and the commutator, an arm provided with a central brush passageway therethrough to accommodate the brush, a spring connected to said arm for biasing the brush against the commutator, the second of said studs being positioned adjacent to the end of said arm remote from said first stud to provide a maximum leverage relative to said passageway, a pair of bolts adapted to secure said arm to said pair of studs, said bolts being insulated from the machine to prevent grounding of the brush therethrough, said arm being provided with a first aperture centered over said first stud and adapted to fit tightly one of said bolts to pivotably support said arm on said first stud, said arm being provided with a second enlarged aperture positioned over said second stud and adapted to fit loosely the other of said bolts, said arm being provided with a plurality of pairs of equally spaced apart recesses surrounding said second aperture, and a locking plate provided with a central opening adapted to fit tightly said other bolt and provided with a pair of detents adapted to selectively engage one pair of said recesses, said pairs of recesses being arranged in conjunction with said plate to secure said other bolt in a plurality of positions relative to said second aperture whereby said brush holder may be secured in a plurality of angular positions relative to said commutator.

No references cited. 

